Self-aligning optical micro-mechanical device package

ABSTRACT

A package for optical micro-mechanical devices including a die with one or more optical micro-mechanical devices on a first surface of a substrate. The first surface includes a die reference surface. One or more optical interconnect alignment mechanisms are formed in the first surface of the die. The optical interconnect alignment mechanisms are positioned to optically couple an optical interconnect with one or more of the optical micro-mechanical devices on the die. A package frame including an aperture and a package frame reference surface proximate the aperture is adapted to receive the die reference surface such that the optical micro-mechanical devices are located in the aperture. One or more optical interconnect alignment mechanisms are formed in the package frame. The optical interconnect alignment mechanisms on the package frame are positioned to align with corresponding optical interconnect alignment mechanisms on the die when the die reference surface is engaged with the package frame reference surface.

FIELD OF THE INVENTION

The present invention relates to corresponding alignment mechanisms onboth the package frame and the die to capture and align the opticalfibers and/or lens with the optical micro-mechanical devices.

BACKGROUND OF THE INVENTION

Fabricating complex micro-electro-mechanical systems (MEMS) andmicro-optical-electro-mechanical systems (MOEMS) devices represents asignificant advance in micro-mechanical device technology. Presently,micrometer-sized analogs of many macro-scale devices have been made,such as for example hinges, shutters, lenses, mirrors, switches,polarizing devices, and actuators. These devices can be fabricated, forexample, using Multi-user MEMS Processing (MUMPs) available from CronosIntegrated Microsystems located at Research Triangle Park, NorthCarolina.

One method of forming a MEMS or MOEMS device involves patterning thedevice in appropriate locations on a substrate. As patterned, the devicelies flat on top of the substrate. For example, the hinge plates of ahinge structure or a reflector device are both formed generally coplanarwith the surface of the substrate using the MUMPs process. Applicationsof MEMS and MOEMS devices include, for example, data storage devices,laser scanners, printer heads, magnetic heads, micro-spectrometers,accelerometers, scanning-probe microscopes, near-field opticalmicroscopes, optical scanners, optical modulators, micro-lenses, opticalswitches, and micro-robotics.

Packaging MEMS devices presents unique problems due to the physicallyactive nature of the microstructures. To maintain a stable environmentand to keep out dust particles, corrosive and/or potentially foulingvapors, etc., the micro-machined structures must be enclosed within asealed package. A sealed package also minimizes the risk of physicaldamage during handling or operation. Traditional integrated circuitencapsulation methods such as epoxy resin potting and thermoplasticinjection molding, while useful with integrated circuits, which have nomoving parts, are incapable of use directly with micro-machinedstructures. The encapsulant must not contact the active portions of themicro-machined structure. Moreover, common encapsulation techniques suchas injection molding, often requiring pressures of 1000 psi, wouldeasily crush the microstructure.

One application for micro-machined structures is in connection withprocessing optical signals, such as optical switches, wavelengthspecific equalizers, polarization mode dispersion compensators, and thelike. These applications, however, require coupling optical fibers withthe packaged micro-machined structures. Various techniques are known forpackaging MEMS devices, such as disclosed in U.S. Pat. No. 6,146,917(Zhang et al.) EP0852337; and EP1057779. None of these packagingtechniques, however, teach coupling optical fibers to the MEMS device.

BRIEF SUMMARY OF THE INVENTION

The present invention relates to alignment mechanisms on both thepackaged and the die containing the optical micro-mechanical devices.The alignment mechanism is adapted to receive and capture an opticalinterface, such as an optical fiber or optical lens. The package framecontains alignment mechanisms, such as V-grooves, that horizontallymatch with corresponding alignment mechanisms on the die. Vertically,the V-grooves are designed to align the centerline of the optical fibersand/or lenses to the active surface of the optical micro-mechanicaldevices.

In one embodiment, the package for optical micro-mechanical devicesincludes a die with one or more optical micro-mechanical devices on afirst surface of a substrate. The first surface includes a die referencesurface. One or more optical interconnect alignment mechanisms areformed in the first surface of the die. The optical interconnectalignment mechanisms are positioned to optically couple an opticalinterconnect with one or more of the optical micro-mechanical devices onthe die. A package frame comprising an aperture and a package framereference surface proximate the aperture is adapted to receive the diereference surface such that the optical micro-mechanical devices arelocated in the aperture. One or more optical interconnect alignmentmechanisms are formed in the package frame. The optical interconnectalignment mechanisms on the package frame are positioned to align withcorresponding optical interconnect alignment mechanisms on the die whenthe die reference surface is engaged with the package frame referencesurface.

In one embodiment, distal ends of one or more optical interconnects arecaptured between in the optical interconnect alignment mechanisms on thepackage frame and the corresponding optical interconnect alignmentmechanisms on the die when the die reference surface is engaged with thepackage frame reference surface.

The optical interconnect comprises one of an optical fiber, an opticallens or a combination thereof. The optical interconnect alignmentmechanisms are typically V-grooves. The die reference surface and/or thepackage frame reference surface can be an optical interface referenceplane.

One or more contact pads are typically interposed between the diereference surface and the package frame reference surface. The contactpads electrically couple one or more optical micro-mechanical deviceswith external electrical contacts. The contact pads can alsoelectrically couple one or more optical micro-mechanical devices with aflexible circuit member. In one embodiment, the contact padselectrically couple one or more optical micro-mechanical devices withcontact pads located on the package frame reference surface. In anotherembodiment, a flexible circuit extends across a rear surface of the die.One or more vias extend through the die and electrically couple theoptical micro-mechanical devices to the flexible circuit.

In one embodiment, the die has a shoulder region adjacent to the opticalmicro-mechanical devices. Electrical traces extend from the opticalmicro-mechanical devices to the shoulder region. A flexible circuitcoupled to the traces is located between the shoulder region and theoptical interface reference plane.

In another embodiment, the package frame includes one or more alignmentposts position to engage with the die reference surface. A cavity isprovided adjacent to the alignment posts on a side opposite theaperture. A flexible circuit can extend through the cavity toelectrically couple with contact pads on the die reference surface. Anadhesive can be located in the cavity to retain the die to the alignmentposts.

The aperture can be a rectangular shape or any other shape. A toolingfixture, such as a heat sink and/or tooling post are preferably locatedon the rear surface of the die. Alternatively, the tooling post islocated on a rear surface of the die. An encapsulating material can beused to seal the die to the package frame. A cover seals the die to thepackage frame.

The present invention is also directed to an optical communicationsystem including at least one packaged optical micro-mechanical devicein accordance with the present invention.

The present invention is also directed to a method of packaging opticalmicro-mechanical devices. One or more optical interconnect alignmentmechanisms are prepared on a die reference surface of the die. Theoptical interconnect alignment mechanisms are positioned to opticallycouple an optical interconnect with one or more optical micro-mechanicaldevices on the die. A package frame is prepared comprising an apertureand a package frame reference surface proximate the aperture adapted toreceive the die reference surface such that the optical micro-mechanicaldevices are located in the aperture. One or more optical interconnectalignment mechanisms are prepared in the package frame. The opticalinterconnect alignment mechanisms on the package frame are positioned toalign with corresponding optical interconnect alignment mechanisms onthe die when the die reference surface is engaged with the package framereference surface.

The method includes positioning one or more optical interconnects in theoptical interconnect alignment mechanisms on the package frame andengaging the die reference surface with the package frame referencesurface to capture the optical interconnects. One or more of the opticalinterconnects are captured between in the optical interconnect alignmentmechanisms on the package frame and the corresponding opticalinterconnect alignment mechanisms on the die. In one embodiment, the dieis sealed to the package frame using an encapsulating material. Inanother embodiment, a flexible circuit is electrically coupled to thedie.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWING

Further features of the invention will become more apparent from thefollowing detailed description of specific embodiments thereof when readin conjunction with the accompany drawings.

FIG. 1 is a top view of a package frame in accordance with the presentinvention.

FIG. 2 is a side sectional view of a packaged micro-mechanical deviceusing the package frame of FIG. 1 in accordance with the presentinvention.

FIG. 3 is a side sectional view of the packaged micro-mechanical deviceof FIG. 2 taken at a different location.

FIG. 4 is a side sectional view of a packaged micro-mechanical devicehaving mounting or contact pads in accordance with the presentinvention.

FIG. 5 is a side sectional view of a packaged micro-mechanical devicehaving alignment posts in accordance with the present invention.

FIG. 6 is a top view of an alternate package frame in accordance withthe present invention.

FIG. 7 is a side sectional view of a micro-mechanical device packaged inthe package frame of FIG. 6.

FIG. 8 is an alternate micro-mechanical device packaged in the packageframe of FIG. 6.

FIG. 9 is a top view of a packaged micro-mechanical device.

FIG. 10 is a sectional view of the packaged micro-mechanical device ofFIG. 9.

FIG. 11 is a top view of a packaged micro-mechanical device inaccordance with the present invention.

FIG. 12 is a side sectional view of the packaged micro-mechanical deviceof FIG. 11.

FIG. 13 is a bottom view of the packaged micro-mechanical device of FIG.11.

DETAILED DESCRIPTION OF THE INVENTION

Various technologies for fabricating micro-mechanical devices areavailable, such as for example the Multi-User MEMS Processes (MUMPs)from Cronos Integrated Microsystems located at Research Triangle Park,North Carolina. One description of the assembly procedure is describedin “MUMPs Design Handbook,” revision 6.0 (2001) available from CronosIntegrated Microsystems. As used herein, “micro-mechanical device”refers to micrometer-sized mechanical, opto-mechanical,electromechanical, or opto-electro-mechanical device constructed on thesurface of a substrate.

Polysilicon surface micromachining adapts planar fabrication processsteps known to the integrated circuit (IC) industry to manufacturemicro-electro-mechanical or micro-mechanical devices. The standardbuilding-block processes for polysilicon surface micromachining aredeposition and photolithographic patterning of alternate layers oflow-stress polycrystalline silicon (also referred to a polysilicon) anda sacrificial material (e.g. silicon dioxide or a silicate glass). Viasetched through the sacrificial layers at predetermined locations provideanchor points to a substrate and mechanical and electricalinterconnections between the polysilicon layers. Functional elements ofthe device are built up layer by layer using a series of deposition andpatterning process steps. After the device structure is completed, itcan be released for movement by removing the sacrificial material usinga selective etchant such as hydrofluoric acid (HF) which does notsubstantially attack the polysilicon layers (referred to herein as“release”). Where a single substrate contains multiplemicro-electro-mechanical or micro-mechanical devices, the substrate orwafer is typically cut into discrete pieces before release.

The result is a construction system generally including a first layer ofpolysilicon which provides electrical interconnections and/or a voltagereference plane, and additional layers of mechanical polysilicon whichcan be used to form functional elements ranging from simple cantileveredbeams to optical micro-mechanical devices. As used herein, “opticalmicro-mechanical device” refers to a micro-mechanical device formanipulating optical signals, including without limitation opticalswitches, near-field optical microscopes, optical scanners, opticalmodulators, micro-lenses, wavelength specific equalizers, polarizationmode dispersion compensators, and the like. Examples of opticalmicro-mechanical devices are shown in U.S. patent applications entitledOptical Switch Based On Rotating Vertical Micro-Mirror filed Jan. 29,2001, Ser. No. 09/771,757; MEMS-Based Polarization Mode DispersionCompensator filed Jan. 29, 2001, Ser. No. 09/771,765; and MEMS-BasedWavelength Equalizer filed Oct. 31, 2000, Ser. No. 09/702,591.

FIG. 1 is a top view of a package frame 20 for packaging opticalmicro-mechanical devices in accordance with the present invention. Thepackage frame 20 includes an aperture 22 for receiving a die 24containing one or more optical micro-mechanical devices in a flip-chipconfiguration. The aperture 22 can be virtually any shape. Flip-chipbonding involves bonding the die 24 face down on package frame referencesurface 28. Die 24 is shown in phantom to indicate the interface of thepackage frame 20 with the die 24. As used herein, “die” refers to asubstrate containing one or more optical micro-mechanical devices.

In one embodiment, top surface 26 of the package frame 20 includes aplurality of traces 30 electrically coupled to contact pads 32 thatterminate in the package frame reference surface 28. In embodimentswhere the entire top surface 26 is planarized, the package framereference surface 28 may be the entire top surface 26. The contact pads32 electrically couple with corresponding contact pads on the die 24.The present flip-chip configuration allows placement of contact padsover the top surface of the die 24, resulting in a significant increasein density and input/output connections. In the embodiment of FIG. 1,the top surface 26 includes a series of optical interconnect alignmentmechanisms 29, such as a V-groove, adapted to align an opticalinterconnect, such as an optical fiber, with aperture 22 and the die 24.The optical fiber can be bare optical fiber, an optical fiber with lensattached (such as GRIN lens), an optical fiber surrounded by ferruleswith or without a lens, or a combination thereof.

The package frame 20 can be constructed of a variety of materials,including ceramics, metals and plastics. The ease of shaping along withreliability and attractive material properties such as electricalinsulation and hermetic sealing, have made ceramics a mainstay inelectronic packaging. Ceramics are widely used in multi-chip modules andadvanced electronic packages such as ball grid arrays. Ceramics providea combination of electrical, thermal and mechanical properties desirablefor packaging micro-mechanical devices. The coefficient of thermalexpansion (CTE) for ceramic packaging can be designed to closely matchthe CTE of the die containing the micro-mechanical devices.

Metal packages are practical because they are robust and easy to produceand assemble. Metal packages are attractive for optical micro-mechanicaldevice packaging for the same reason they were adopted by the integratedcircuit industry. Metal packages satisfy the pin count requirement ofmost optical micro-mechanical device applications and they can beprototyped on small volumes with a short turn-around time. Metalpackaging also provides a hermetic seal.

Molded plastic packages are typically not hermetic like metal orceramic. Plastic packages are attractive because of the relatively lowcost and ease of manufacturing.

FIGS. 2 and 3 are side sectional views of a packaged opticalmicro-mechanical device 40 using the package frame 20 shown in FIG. 1.Die reference surface 42 on the die 24 is bonded to package framereference surface 28 on the package frame 20. In the embodiment of FIG.2, the interface of the die reference surface 42 and package framereference surface 28 comprises an optical interface reference plane 44that is used to align ferrules 76 containing optical fibers 72 andassociated lenses 70 with optical micro-mechanical devices 43 (see FIG.3). The optical micro-mechanical devices 43 are illustrated in phantomso as to not obscure the lenses 70. Only some of the opticalmicro-mechanical devices 43 are shown so that the lenses 70 and otherfeatures are visible. As used herein, “die reference surface” refers tothe top surface of a die upon which the optical micro-mechanical devicesare constructed. The “optical interface reference plane” refers to areference plane adjacent to the micro-mechanical devices, such as thedie reference surface, the package frame reference surface, or somereference plane located therebetween. By locating the optical interfacereference plane adjacent to the optical micro-mechanical devices 43,tolerance build-up is minimized.

In the embodiment illustrated in FIGS. 2 and 3, V-grooves 50 are formedin top surface 26 of the package frame 20. The depth of the V-grooves 50are accurately formed to provide the vertical alignment of the fibers72, ferrules 76 and lenses 70 with the micro-mechanical devices 43. Inone embodiment, the V-grooves allow the lenses 70 to form a tangentialrelationship with the optical interface reference plane 44. In theillustrated embodiment, groups of lenses 70 are arranged perpendicularto each other, but still tangential to the optical interface referenceplane 44. V-Grooves can be formed using mechanical or chemical materialremoval techniques, such as etching.

The die 24 and the V-grooves 50 capture and accurately align the lenses70 of the ferrules 76 with the optical interface reference plane 44 andthe optical micro-mechanical devices 43. The embodiment of FIGS. 2 and 3is particularly well suited when the active optical surfaces on theoptical micro-mechanical devices 43 extend above the die referencesurface 42 an amount generally corresponding to half the diameter of thelenses 70. In that configuration, the lenses 70 are centered withrespect to the micro-mechanical devices 43.

In one embodiment of the present packaged optical micro-mechanicaldevice 40, electrical interconnects are provided by flex circuit 60. Theflex circuit 60 electrically connects the die 24 to the package frame20. In another embodiment, the flex circuit 60 extends along the topsurface 26 to the edge of the package frame 20. Various techniques canbe used to electrically couple the flex circuit 60 with the die 24, suchas solder reflow, conductive adhesives, tape automated bonding,thermo-compression, and the like.

In the illustrated embodiment, external electrical contacts 74 areoptionally provided around the perimeter of the package frame 20 toelectrically couple the flex circuit 60 and the optical micro-mechanicaldevices 43 to a printed circuit board or other electrical device. A widevariety of electric contact configurations can be used to deliverelectric current to the die 24, such as a ball grid array (BGA), landgrid array (LGA), plastic leaded chip carrier (PLCC), pin grid array(PGA), edge card, small outline integrated circuit (SOIC), dual in-linepackage (DIP), quad flat package (QFP), leadless chip carrier (LCC),chip scale package (CSP).

Rear surface 55 of the die 24 includes a tooling fixture 56, such as aheat sink and/or a tooling post. In the embodiment of FIGS. 2 and 3, thefunctions of the heat sink and the tooling post are combined in singlestructure. The tooling fixture 56 can be formed from a single piece ofmaterial or separate components. In one embodiment, the rear surface 55is attached to the tooling fixture 56 prior to the individual die 24being cut from the wafer. The tooling fixture 56 are preferably attachedprior to the optical micro-mechanical devices 43 being released from thedie 24. The tooling fixture 56 can be attached to the die 24 using avariety of adhesives.

The tooling fixture 56 provide convenient handles for users andautomated fabrication equipment to handle the die 24 without damage tothe optical micro-mechanical devices 43. Once the tooling fixture 56 isattached, the front surface or die reference surface 42 are unobstructedand available for HF etching and engagement with the package frame 20.Once attached to the package frame 20, the tooling fixture 56 becomes anintegral part of the packaged optical micro-mechanical device 40.

Upper frame member 48 and cover 49 seal the die to the package frame 20.The upper frame member 48 and cover 49 can be formed as a singlecomponent or multiple components. The tooling fixture 56 facilitateshandling of the die 24 during the packaging process. Compliant thermallyconductive material 52 is preferably located between the tooling fixture56 and the cover 49 to conduct heat away from the packaged opticalmicro-mechanical device 40. An encapsulating material 62 can optionallybe placed over the die 24 and/or the tooling fixture 56 to further sealthe aperture 22 from environmental contamination. Bottom cover 54 sealsthe aperture 22 opposite the die 24. Aperture 22 is optionally a vacuumor can be filled with a gas, such as nitrogen or argon.

True hermetic sealed packages are assumed to be made of metal ornon-organic materials. For some applications of the packaged opticalmicro-mechanical device 40, a hermetic seal is not required. Forexample, an overall enclosure may provide the required protection forthe packaged optical micro-mechanical device 40. In these embodiments,only the encapsulating material 62 is used and the upper frame member 48and cover 49 are omitted. The encapsulating material 62 is preferably alow out-gassing on cure elastomer that minimizes condensation on theoptical micro-mechanical devices 43, such as epoxy, epoxy with silicafibers, epoxy cresol novolac polymer.

The embodiments of FIGS. 2 and 3 illustrate the die 24 bonded directlyto the package frame reference surface 28. FIG. 4 illustrates analternate embodiment in which the die reference surface 42 on the die 24and/or the package frame reference surface 28 include one or morecontact pads 80, 82. The contact pads 80, 82 can be simply used toaccurately align and mount the die 24 to the package frame referencesurface 28. In another embodiment, the contact pads 80, 82 provide anelectrical interconnection between the optical micro-mechanical devices43 on the die reference surface 42 and the contact pads 32 (see FIG. 1)on the package frame 20. The contact pads 80, 82 can be constructed fromsolder, conductive adhesive or a variety of other conductive materials.As used herein, “contact pads” refers to a mechanical and/or electricalinterface between a die and a package frame.

Although the embodiment of FIG. 4 shows two contact pads 80, 82, asingle bonding pad may be located on either the die reference surface 42or the package frame reference surface 28. In the embodiment of FIG. 4,optical interface reference plane 84 is preferably coplanar with the diereference surface 42. In another embodiment, the optical interfacereference plane 84 can be located anywhere between the die referencesurface 42 and the package frame reference surface 28. For example, theoptical interface reference plane can be located at the interfacebetween the contact pads 80 and 82. The optical interface referenceplane 84 is preferably adjacent to the optical micro-mechanical devices43. In the embodiment of FIG. 4, the functions of the heat sink and thetooling post are combined in single structure 85. Although FIG. 4illustrates the tooling fixture 85 as a rectangular block, the shape canvary depending upon the application, the nature of the package frame,the type of optical micro-mechanical devices, the type of cover used,and other factors.

FIG. 5 illustrates an alternate package frame 86 with one or morebonding and alignment posts 88 and an adjacent cavity 90. In oneembodiment, the cavity 90 is used to electrically couple flex circuit 92to contact pads on die reference surface 42. In the embodiment of FIG.5, the die reference surface 42 and the package frame reference surfaces28 are coplanar and preferably comprise an optical interface referenceplane 98. In another embodiment, the cavity 90 can be filled with anadhesive 94 used to retain the die 24 to the alignment posts 88.Locating the adhesive 94 in the cavity 90 permits direct physicalcontact between the die reference surface 42 and tops 96 of thealignment posts 88, thereby minimizing misalignment.

In the embodiment of FIG. 5, a compliant thermally conductive material91 optionally surrounds tooling post 93. The material 91 can operate asa heat sink and/or to buffer the die 24 from shock loads. Tooling post93 optionally contacts or engages with inside surface of cover 95 tofurther secure the die 24 to the package frame 86.

Careful consideration must be given to die attachment because itstrongly influences thermal management and stress isolation. The bondmust not crack or suffer from creep over time. Die attachment processestypically employ metal alloys or organic or inorganic adhesives asintermediate bonding layers. Metal alloys typically include all forms ofsolder, including eutectic and non-eutectic solders. Organic adhesivesinclude epoxies, silicones, and polyimides. The choice of a solder alloydepends on having suitable melting temperature and mechanicalproperties. Solder firmly attaches the die to the package and normallyprovides little or no stress isolation when compared to organicadhesives. However, the bond is very robust and can sustain a large,normal pull force. Metal solders are typically unsuitable if the packageframe includes contact pads in the package frame reference surfacepositioned to electrically couple with the die. The large mismatch incoefficient of thermal expansion between the die and the package frametypically results in undesirable stress and can cause cracks in thebond.

FIG. 6 is a top view of an alternate package frame 100 having anaperture 102 with a more complex shape. Die 104 is shown schematicallyto indicate the interface of the package frame reference surface 106with the die 104. V-grooves 108 are directed to the aperture 102 fromall four sides. Portions or arms 110A, 110B, 110C, 110D of the aperture102 allow the optical fibers and corresponding lenses to terminatebefore the edge of the die 104 is reached (see FIGS. 7 and 8). As willbe discussed below, the height of the lens on the optical fiber can beadjusted relative to the die reference surface to compensate for theheight of the optical micro-mechanical devices by controlling the depthof the V-grooves 108.

FIG. 7 is a side sectional view of a packaged optical micro-mechanicaldevice 120 with die mounting surface 122 bonded to package framereference surface 106 along optical interface reference plane 124.V-grooves 108 have a depth such that lenses 126 and ferrules 144containing optical fibers 146 extend both above and below the opticalinterface reference plane 124. The outside diameter of the ferrules 144preferably match the outside diameter of the lenses 126 so that theV-groove can be one constant depth. The depth of the grooves 108 can beused to adjust the position of the lenses 126 relative to the opticalinterface reference plane 124. That is, the lenses 126 can be positionedrelative to the optical interface reference plane 124 independent of thedie reference surface 122. By changing the depth of the V-grooves 108,the package frame 100 of FIG. 6 can be used with a variety of dies 104while still aligning the lenses 126 with the optical micro-mechanicaldevices (see FIG. 3). The embodiment of FIG. 7 can also be used with thecontact pads 80, 82 of FIG. 4.

The package frame 100 preferably includes a bottom cover 130 extendingover aperture 102. In the embodiment illustrated in FIG. 7, top cover132 is a separate component bonded to the package frame 100 using avariety of techniques, such as solder, brazing, adhesives, etc.Electrical connections are made to the die 104 using flex circuit 136.In the embodiment illustrated in FIG. 7, the flex circuit 136 extendsalong back surface 138 of the die 104. Vias 140 formed in the die 104electrically couple the flex circuit 136 with the opticalmicro-mechanical devices (see FIG. 3) on the die reference surface 122.A pin grid array 142 or a variety of other connectors can be used forcoupling the flex circuit 136 to other electrical components. Any of theelectrical interconnect techniques disclosed herein can be used with theembodiment of FIG. 7.

FIG. 8 is a side sectional view of an alternate packaged opticalmicro-mechanical device 150 using the package frame 100 of FIG. 6. Die152 is formed with a shoulder 154 around at least a portion of itsperimeter. Electrical traces extend along front surface 156 of the die152 to the shoulder 154. Flex circuit 158 electrically couples with thecontact pads on the shoulder 154 of the die 152. Die reference surface160 couples with package frame reference surface 106 to form an opticalinterface reference plane 162, as discussed above. Tooling fixture 164and encapsulating material 166 are optionally provided with the packagedoptical micro-mechanical device 150. The encapsulating material 166 canoptionally be thermally conductive.

FIGS. 9 and 10 are top and side sectional views of a packaged opticalmicro-mechanical device 200 in accordance with the present invention.Die reference surface 202 is bonded to package frame reference surface204 (with or without the contact pads of FIG. 4) to form an opticalinterface reference plane 206. V-grooves 208 are formed in MEMS die 210to vertically and horizontally center lenses 230 to the centerline ofoptical micro-mechanical devices 224. The V-grooves 208 in the die 210can be machined or formed using the MUMPs process.

The package frame 216 contains V-grooves 212 that horizontally match tothose on the die 210. Vertically, the V-grooves 208, 212 are designed toalign the centerline of the lenses 230 to the centerline of the fiberferrules 232. The depth of the grooves 208, 212 can be adjusted so thatthe location of lenses 230 relative to the optical interface referenceplane 206 can be optimized for the particular optical micro-mechanicaldevices 224.

The outside diameter of the fiber ferrule 232 preferably matches theoutside diameter of the lenses 230, so a single size V-groove 212 can beformed in the package frame 216. The combination of the two sets ofV-grooves 208, 212 align the die 210 to the package frame 216 using thelenses 230 and/or ferrules 232 as the datum in all three orthogonalaxes. Simultaneously, when the die reference surface 202 is engaged withthe package frame reference surface 204, the lenses 230 are captured andautomatically aligned with the optical micro-mechanical devices 224 onthe die 210.

The embodiment of FIGS. 9 and 10 optionally includes a heat sink 220with a tooling post 222. The heat sink 220 optionally includes extensiontabs 238 that extend beyond the perimeter of the die 216. The extensiontabs 238 can be any of a variety of shapes. Upper frame member 234 andcover 236 attach to the package frame 216 to protect the die 210. Athermally conductive encapsulating material may optionally be providedbetween the heat sink 220 and the cover 236.

FIGS. 11-13 illustrate an alternate packaged optical micro-mechanicaldevice 300 in accordance with the present invention. A pair of ferrules302 containing optical fibers 304 with corresponding lenses 306 arepositioned on each side of the die 308. The lenses 306 terminate beforethe edge of the die 308. The eight lenses 306 and associated opticalfibers 304 are for illustration purposes only and the number of fiberscan vary depending on the application.

Optical micro-mechanical devices 310 are positioned in cross-shapedaperture 312 so that only the corners of the die 308 contact packageframe 314 (see e.g., FIG. 6). Die reference surface 320 comprises theoptical interface reference plane 330. The gaps created in the portions316A, 316B, 316C, 316D of the aperture 312 permit a flexible circuit 318to electrically couple with contact pads on the die reference surface320 (see FIG. 13) and extend out along top surface 322 of the packageframe 314 (see FIG. 11). For the sake of clarity, upper package frame324, cover 326 and tooling fixture 328 are only shown in FIG. 12. Theupper package frame 324 and cover 326 can be formed from a single pieceof material or can be separate components. A thermally conductiveelastomeric material is optionally provided between the tooling fixture328 and the die 308 and/or the tooling fixture 328 and the cover 326.

All of the patents and patent applications disclosed herein, includingthose set forth in the Background of the Invention, are herebyincorporated by reference. Although specific embodiments of thisinvention have been shown and described herein, it is to be understoodthat these embodiments are merely illustrative of the many possiblespecific arrangements that can be devised in application of theprinciples of the invention. Numerous and varied other arrangements canbe devised in accordance with these principles by those of ordinaryskill in the art without departing from the scope and spirit of theinvention.

What is claimed is:
 1. A package for optical micro-mechanical devices,comprising: one or more optical micro-mechanical devices on a firstsurface of a die, the first surface of the die comprising a diereference surface; one or more optical interconnect alignment mechanismsformed in the first surface of the die, the optical interconnectalignment mechanisms being positioned to optically couple an opticalinterconnect with one or more of the optical micro-mechanical devices onthe die; a package frame comprising an aperture and a first surface, thefirst surface of the package frame comprising a package frame referencesurface proximate the aperture, wherein the package frame referencesurface is adapted to allow the die reference surface to be mounted tothe package frame reference surface such that the opticalmicro-mechanical devices are located in the aperture; and one or moreoptical interconnect alignment mechanisms formed in the first surface ofthe package frame, the optical interconnect alignment mechanisms on thepackage frame being positioned to align with corresponding opticalinterconnect alignment mechanisms on the die when the die referencesurface is mounted to the package frame reference surface.
 2. Theapparatus of claim 1 comprising distal ends of one or more opticalinterconnects captured between in the optical interconnect alignmentmechanisms on the package frame and the corresponding opticalinterconnect alignment mechanisms on the die when the die referencesurface is engaged with the package frame reference surface.
 3. Theapparatus of claim 1 wherein the optical interconnect comprises one ofan optical fiber, an optical lens, or a combination thereof.
 4. Theapparatus of claim 1 wherein the optical interconnect alignmentmechanism on the package frame terminate adjacent to the aperture. 5.The apparatus of claim 1 wherein the optical interconnect alignmentmechanisms comprise V-grooves.
 6. The apparatus of claim 1 wherein thedie reference surface comprises an optical interface reference plane. 7.The apparatus of claim 1 wherein the package frame reference surfacecomprises an optical interface reference plane.
 8. The apparatus ofclaim 1 comprising one or more contact pads interposed between the diereference surface and the package frame reference surface.
 9. Theapparatus of claim 8 wherein the contact pads electrically couple one ormore optical micro-mechanical devices with external electrical contacts.10. The apparatus of claim 8 wherein the contact pads electricallycouple one or more optical micro-mechanical devices with a flexiblecircuit member.
 11. The apparatus of claim 8 wherein the contact padselectrically couple one or more optical micro-mechanical devices withcontact pads located on the package frame reference surface.
 12. Theapparatus of claim 1 wherein the aperture comprises a rectangular shape.13. The apparatus of claim 1 wherein the aperture comprises a complexshape.
 14. The apparatus of claim 1 comprising a tooling fixture on arear surface of the die.
 15. The apparatus of claim 14 wherein thetooling fixture comprises a heat sink.
 16. The apparatus of claim 1comprising a tooling post on a rear surface of the die.
 17. Theapparatus of claim 1 comprising an encapsulating material sealing thedie to the package frame.
 18. The apparatus of claim 1 comprising acover sealing the die to the package frame.
 19. The apparatus of claim 1wherein the aperture comprises a cover.
 20. The apparatus of claim 1comprising a flexible circuit electrically coupled to the die.
 21. Theapparatus of claim 1 comprising electric traces on the package frame,the electric traces electrically coupled to contact pads in the packageframe reference surface.
 22. The apparatus of claim 1 comprising: aflexible circuit extending across a rear surface of the die; and one ormore vias extending through the die and electrically coupling theoptical micro-mechanical devices to the flexible circuit.
 23. Theapparatus of claim 1 comprising: a shoulder region adjacent to theoptical micro-mechanical devices; electrical traces extending from theoptical micro-mechanical devices to the shoulder region; and a flexiblecircuit located between the shoulder region and the optical interfacereference plane, the flexible circuit being electrically coupled to thetraces.
 24. The apparatus of claim 1 wherein the package framecomprises: one or more alignment posts position to engage with the diereference surface; and a cavity adjacent to the alignment posts on aside opposite the aperture.
 25. The apparatus of claim 24 comprising aflexible circuit extending through the cavity electrically couples withcontact pads on the die reference surface.
 26. The apparatus of claim 24comprising an adhesive located in the cavity sufficient to retain thedie to the alignment posts.
 27. The apparatus of claim 1 comprising anoptical communication system including at least one packaged opticalmicro-mechanical device.
 28. A method of packaging opticalmicro-mechanical devices, comprising: preparing one or more opticalinterconnect alignment mechanisms on a die reference surface of the die,the optical interconnect alignment mechanisms being positioned tooptically couple an optical interconnect with one or more opticalmicro-mechanical devices on the die; preparing a package framecomprising an aperture and a package frame reference surface proximatethe aperture adapted to allow the die reference surface to be mounted tothe package frame reference surface such that the opticalmicro-mechanical devices are located in the aperture; and preparing oneor more optical interconnect alignment mechanisms in package frame, theoptical interconnect alignment mechanisms on the package frame beingpositioned to align with corresponding optical interconnect alignmentmechanisms on the die when the die reference surface is mounted to thepackage frame reference surface.
 29. The method of claim 28 comprisingthe steps of: positioning one or more optical interconnects in theoptical interconnect alignment mechanisms on the package frame; andengaging the die reference surface with the package frame referencesurface to capture the optical interconnects.
 30. The method of claim 28comprising the step of capturing one or more optical interconnectsbetween in the optical interconnect alignment mechanisms on the packageframe and the corresponding optical interconnect alignment mechanisms onthe die.
 31. The method of claim 28 wherein the step of preparing one ormore optical interconnect alignment mechanisms in the first surface ofthe die comprises forming V-grooves.
 32. The method of claim 28 whereinthe step of preparing one or more optical interconnect alignmentmechanisms in package frame terminating adjacent to the aperturecomprises forming V-grooves.
 33. The method of claim 28 comprisingattaching a tooling fixture on a rear surface of the die.
 34. The methodof claim 33 wherein the tooling fixture comprises a tooling post and aheat sink.
 35. The method of claim 28 comprising sealing the die to thepackage frame using an encapsulating material.
 36. The method of claim28 comprising electrically coupling a flexible circuit to the die. 37.The method of claim 28 comprising the steps of: preparing one or morevias through the die electrically coupled to the opticalmicro-mechanical devices; and electrically coupling a flexible circuitto one or more of the vias.